On Sun, 2 Apr 1995, Andrew K. Groves wrote:
> In article <Pine.SOL.3.91.950401211906.17841A-100000 at corona>, Patrick
> O'Neil <patrick at corona> wrote:
>> > The DNA and proteins that first made me no longer exist, as they were
> > the precise strands of DNA and extant proteins within the zygote that led
> > to me. Those original cells and their contents have long ceased to exist
> > ....
>> We are dealing with a problem of definition here. Dr. Bogler and myself
> are using a set of precise definitions (which I will outline below) that
> ...divide and rapidly fill up the area on the dish. At this point, they
> will
> stop dividing. They are said to be QUIESCENT. If you dissociate the cells
> on the dish, and replate them at a lower density, the cells will start
> dividing again... You can repeat this process between four and six
> times (by
> which time each of your founder cells will have divided probably between
> 20 and 30 times). At this point, the cells once more stop dividing, and
> become noticeably flattened. They cannot now be induced to divide any
> more. They are said now to be SENESCENT. Senescent cells do not die...
I apologize for picking at details, particularly amongst a group that
basically knows what it is talking about (vs those in sci.cryonics and
related). Even a senescent cell cannot continue indefinitely since
stochastic processes, as well as environmental effectors work to cleave,
dimerize, hydrolyze, radicalize, etc, etc, DNA, proteins, and lipids and
that the cellular house-keeping genes and proteins are not 100% perfect
in detection nor repair/maintenance. Thus, even a senescent cell is
going to die no matter how well it is treated - BUT it is not, certainly,
as subject to irreparable damage and alterations as is any actively
replicating cell and is not subject to all the same problems. In the
best of circumstances, a senescent cell may last a long time but it is
definitely a finite period. The only way around this is, paradoxically,
to divide, at least periodically, which brings the dangers inherent in
THIS activity (base misincorporation, template slippage, insertions).
Granted, this should all more likely be directed at another group - that
might envision human immortality rather than a more realistic life
extension or improvement in the quality of normal human lifespan, but it
is these type of nitnoid details that I approach this area from; and from
these little details, I try to pick out areas that might be exploitable
or of interest (balancing just the right amount of replication with
stasis - how and at what level would normal degradative processes be most
optimally balanced though never defeated. From this, you could either
obtain the most life-extension for the buck, as it were, or the best
quality gains). If it seems that I am clouding the issue this is not my
intent.
Patrick